ROUGHED UP: Mets rookie Matt Harvey follows through on a pitch during yesterday’s 7-3 loss to the Padres that capped off an 11-game road trip in which the Amazin’s went 6-5.AP

SAN DIEGO — Matt Harvey is officially a Met. You are not a real Met until you take it on the chin.

There is a lesson to be learned from all of this and general manager Sandy Alderson said it best after the 7-3 loss to the Padres yesterday at Petco Park.

“I think it was a learning experience for him,’’ Alderson told The Post, outside the visitors’ clubhouse. “Just from my observation, without talking with anybody, I thought [Harvey] got away from his strength a little bit. With his power stuff, he has got to work everything else in, but ultimately it has to be about the power stuff.’’

That wasn’t the case yesterday. Harvey’s breaking ball wasn’t at its best and he got hurt with two early changeups. His power stuff had carried him through his Mets debut at Arizona on July 26, with 11 strikeouts and a 3-1 victory.

This time, the big right-hander was down 5-0 after three innings. Harvey (1-2) battled through five, allowing five runs on eight hits. Seven of the hits were extra-base hits. Ouch. Harvey walked one and struck out five.

The rookie is going to have to make adjustments or else it’s going to be a difficult ride. Go with your hard stuff, that’s what got you here, don’t change who you are as a pitcher.

In the first inning, Harvey left up two changeups and paid the price. Everth Cabrera doubled to right and Chase Headley lifted a high-fly off a changeup that kept drifting until it landed on top of the right-field scoreboard for a two-run home run.

In the third, the Padres added three more runs. Carlos Quentin doubled and Yonder Alonso blasted a home run to center to put the Mets down, 5-0.

Harvey could not get his pitches down in the zone. Hurdles are expected and Alderson knows this is all part of the ride.

“I think he learned something today,’’ noted the GM. “It was all the power stuff in Arizona. … Stay with what got you here.’’

Too many young pitchers try to do something different and that never works out, so chalk this up to experience. You got to the dance with power, stay with power.

Against the Diamondbacks on the first game of the Mets’ 11-game sojourn that ended yesterday, Harvey had his adrenaline flowing. He was getting a little extra on his fastball and the Arizona hitters could not lay off the high strikes. Those strikes were a bit too high for the hitters to handle.

This time out, Harvey’s pitches were the perfect height for hitters to crush.

This should be an eye-opening performance for Harvey. Earlier in the week, he told me he was having one little problem with his delivery in that he needed to add a bit more hesitation over the rubber to get the kind of separation and explosion that he needed.

“I need to have almost a hesitation, a pause,” he said. “Sometimes you jump out too fast before your hand gets out of your glove. Sometimes I will go to the plate and my hand is still in my glove, instead of staying over the rubber and getting a release with that hand and arm.’’

Before the game, manager Terry Collins said he was curious to see how Harvey would handle adversity. Collins just didn’t expect all that adversity to hit by the third inning.

The Mets need Harvey to have a bounce-back start Friday against the Braves. That will be his first start at Citi Field. The Mets cannot sell the present because of the way this team has collapsed again. Their hitters could not take advantage of Jason Marquis as the Staten Islander outsmarted the Mets over 6 1/3 innings.

These are all the lessons Harvey cannot learn in the minor leagues. The Padres are not the Yankees, yet they put a hurting on him. They took advantage of his weaknesses. Welcome to the big leagues, kid.

Getting back to his power stuff is just the ticket for Matt Harvey. The GM knows.